The invention resides in a method and apparatus for the detection of hydrocarbons dissolved in bodies of water and a determination of the concentration of the hydrocarbons in the water.
Detection and quantitative determination of hydrocarbons dissolved in liquids, particularly in water such as ground water and seawater, is of great practical importance in many technical areas. This is true for applications in the laboratory as well as in nature. Survey for leakage of gas and crude oil pipelines in the sea is an example of the latter type. Leakage of pipelines and of crude oil deposits will result, among others, in the presence in the seawater of volatile hydrocarbons, of which mostly aliphatic compounds, especially methane, are utilized in the process of determining hydrocarbon presence. In this connection, methods and apparatus suitable for use in connection with remotely controlled operation or fully automatic operation, which permit installation in a remote apparatus carrier and permit continuous or quasi-continuous in-situ measurements, are of particular interest. The presently performed methods of taking water samples from on board a ship and subjecting the samples subsequently to laboratory tests for the determination of methane content in the usual manner does not fulfill the needs.
There is also known (from U.S. Pat. No. 3,436,188) a method, which, in principle, appears to be suitable for in-situ detection of the presence of aliphatic hydrocarbons in water. This method is based on the application of ultrasonic cavitation which results in the formation of hydrogen and hydroxyl ions and the reaction of the hydroxyl ions so formed with any aliphatic hydrocarbons that might be present. In this method there are finally formed aldehydes or ketones which may be determined colorimetrically. The detection, however, is limited to 100 ppm (100:106) so that very small concentrations go unnoticed.
It is the object of the present invention to provide a method and apparatus which permits detection and quantitative determination of volatile hydrocarbons in any type of liquid with a detection sensitivity which is greater by orders of magnitudes, that is, in which the sensitivity limits are in some variations in the ppb range (1:109).